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>You have hit the nail on the head, the binding with hemoglobin is >competitive between oxgyen and carbon monoxide, and thus as long >as the relationship between the partial pressure of monoxide and >oxide remains constant, the amount of hemoglobin bound with monoxide >will remain constant (at least, according to everything I know, and >Bill Hamilton has also been heard to make this same point about >monoxide). Hm. Interesting. But let's think about this a little further. I would establish the following as known truth: 1) each hemoglobin molecule has four binding sites 2) each binding site will accept a single molecule, O2 or CO. 3) O2 binding is regulated, to oversimplify, by ambient pH, resulting in our desired pattern of binding at the alveoli, release in target tissues. 4) CO binding is so thermodynamically favorable that binding is, practically speaking, permanent, essentially removing the bound hemo site from the pool of available transport. 5) ambient pH has little influence on the CO<>hemo binding site, so the molecule remains bound. 5) As with all biochem reactions, we are talking percentages. 6) Red blood cells, and hence hemoglobin, have a functional life-span of 128 days. In general, those bound with CO remain so until the cell is broken down. 7) Smokers, for example, tend to have a higher red blood cell count, but lower available hemoglobin for O2 transport. 8) The only way to improve this is to drive the CO binding reaction with high-pressure O2 SO, Then, I'd suggest the following. 1) as we get partial-pressure increases with depth, relationships remain the same and as such the pressure aspect of the reaction's driving forces remain the same between CO and O2. 2) This results in an increased number of binding sites in the hemoglobin being filled by the two competing molecules, albeit as you suggest in roughly the same relative quantities, as influenced by the relation between their quantities in the inspired mix. 3) When pressure decreases upon decent, O2 binding responds accordingly. 4) CO binding, still the one-way trip, is driven less by the lowered pressure, but the bound molecules remain the same. And then I would conclude: 1) As a one-time shot, I think your point is valid. 2) Over the long term, say from a shop pumping bad air on a regular basis and I didn't know, I would probably end up with a CO poisoning problem. ------------------------------------------------------- scot@bt*.co* Scot Anderson pp000082@in*.co* Voice: 703/761/6536 CIS:74147.2357 Fax: 703/556/9290
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